This invention is addressed to the problem of providing a multiple electrical contact switch with a minimum number of parts capable of responding to the vertical movement of an actuator such as the vertical releasing movement of a push button on a telephone set. Such response can be the opening or the closing of electrical switches from either closed or open positions respectively.
A recent development (Van Cleave et al. U.S. Pat. No. 4,319,102) in electro-mechanical multiple contact switches uses wedges to hold spring contacts in place and operating cards to move the spring contacts to break electrical contact. More specifically, Van Cleave has two blocks which, when one block is inserted into the other, wedge a combed spring contact in place. The teeth of the combed contact are made of an electrical conducting material, and each tooth is one of two conductive parts that make or break contact to perform the switching operation. In the operating card there is a sequence of holes which are positioned at preset locations on the card. When the operating card is inserted below the combed spring contact, the individual teeth are separated from other conductive parts below the card to break electrical contact. However, if there is a hole between the tooth and the corresponding conductive piece, electrical contact is not broken.
Van Cleave is, however, not without its shortcomings. The wedging action in Van Cleave results in bending of the spring contacts possibly precluding their further use. In addition, Van Cleave only discloses a method of sequentially opening a set of switches which are all originally in the closed position. Furthermore, the operating card must be pulled out of position to return all the spring contacts to their original position or rest position wherein the sequence of open and closed contacts acts as if there were no card in contact with the spring contacts. Therefore, if one needed to have the card return to an original position without manually pulling the card, extra springs and parts to locate these extra springs would be necessary. These latter named parts are now used in telephone sets, so that the card can return to its original position when the telephone receiver is off hook.
While there are devices which will put contacts in any sequence of open or closed contacts from any other preset sequence, these devices contain many operating parts. For example, one of the latest developments (Summers U.S. Pat. No. 3,742,485) uses threaded screws, spring biased double throw microswitches with lever arms, a chassis box with four guide plates to hold the microswitches and an operating card.
There is, therefore, a need for a multiple contact switch which will change any preset sequence of opened and closed electrical contacts to any other sequence and return to the preset or original sequence, using a minimum number of parts resulting in reduced costs and ease of assembly.